Olefin polymerization catalysts having a cyclopentadienyl ligand and a conventional phosphinimine ligand are disclosed in a copending and commonly assigned patent application (Stephen et al). The catalysts of the Stephen et al disclosure are highly active for ethylene (co)polymerization, particularly when used in combination with an alumoxane, or an "ionic activator" (or both).
We have now discovered that heterosubstituted phosphinimine ligands may be easily synthesized and can be used as a component of a highly active ethylene polymerization catalyst system.